1. Field of the Invention
The present invention relates to a rotor balancer and a disk drive or driver having the rotor balancer, and more particularly, to a rotor balancer and a disk drive or driver having the rotor balancer which is capable of simplifying a construction of an auto balancing unit for automatically correcting a rotation unbalance occurring when a disk is rotated and a mounting unit for accurately mounting the disk, while reducing a noise and a vibration.
2. Description of the Background Art
Generally, when a rotor for rotating a rotation-object member is rotated, a rotation unbalance may occur from various causes. In order to remove such rotation unbalance problem, a rotor balancer is provided.
The rotor balancer is used for various devices. In the following description, the rotor balancer is taken an example for a disk driver for recording and reproducing a signal on and from a disk such as a CD or a DVD.
Recently, as the disk driver is designed to rotate at a high speed, a disk rotation unbalance problem occurs when a disk is rotated at a high speed.
Such rotation unbalance of the disk makes it difficult to accurately reproduce a signal recorded from the disk or to accurately record a signal on the disk.
The rotation unbalance of the disk is mostly caused due to unbalance of the disk itself (in case that there is a mass eccentricity) when the disk is fabricated, and especially it comes as a more serious problem when the disk is rotated at a high speed.
In addition, the rotation unbalance may occur in case that the disk is not accurately mounted on a turntable.
In order to solve the rotation unbalance of the disk, a balancer is provided to a mounting unit on which the disk is mounted, to a clamp for holding the disk, or to a spindle motor for rotating the disk.
A rotor balancer used for a disk driver in accordance with a conventional art will now be described with reference to the accompanying drawings.
FIG. 1 is a sectional view showing a construction of a disk driver having a rotor balancer in accordance with a conventional art.
As shown in the drawing, at the lower portion of the rotational shaft 1, there are provided a spindle motor 3 for rotating a disk (not shown) by providing a rotor 2 that is rotated along with a rotational shaft 1 and an auto balancing unit for correcting a rotation unbalance when the disk (not shown) is rotated at the side of the spindle motor 3.
The auto balancing unit includes a ball case 4 having a circular racing space, a magnet 5 having a predetermined size positioned at one side in the ball case 4, and a plurality of metallic balls for correcting a rotation unbalance when the disk is rotated positioned at the space 6 between the inner circumferential surface of the ball case 4 and the magnet 5.
The magnet 5 normally serves to prevent the ball 7 from moving freely in the space 6.
The inner circumferential surface of the ball case 4 becomes the outer racing face 8a on which the ball 7 travels, and the surface of the magnet 5 becomes the inner racing face 8b on which the ball 7 travels.
Meanwhile, at the upper portion of the rotational shaft 1, there is provided a mounting unit including a turntable 9 on which a disk (not shown) is mounted, an insert portion formed as an insert cone 10 installed at the upper end of the rotational shaft 1, for accurately fixing the disk (not shown), a mounting ring 11 installed between the turntable 9 and the insert cone 10, and a spring 12 for elastically supporting the mounting ring 11 upwardly.
A friction member 13 is installed at a circumferential portion at the upper surface of the turntable 9, to which a lower surface of the disk is adhered so that the disk is prevented from arbitrarily moving on the turntable 9.
The insert cone 10 and the mounting ring 11 to which a hole (not shown) of the disk is inserted is formed of which the upper circumferential portions are sloped to a predetermined degree, to thereby facilitate insertion of the disk.
The outer diameter of the insert cone 10 is approximately 14.96 mmxcx9c14.99 mm. For reference, the inner diameter of the central hole of the general disk is approximately 15 mmxcx9c15.1 mm.
Accordingly, there is a gap of approximately 10xcx9c40 xcexcm between the inner diameter of the hold of the disk and the outer diameter of the insert cone 10, by which, when the disk is inserted to the insert cone 10 and is clamped by a clamp (not shown), since the disk may be mounted on the turntable 9 in an eccentric state, the disk mounting unit is installed to remove the eccentricity and the disk is centered.
Namely, centering of the disk is made in a manner that in a state that the disk is inserted into the insert cone 10, the mounting ring 11 is upwardly supported by the spring 12 and the claim (not shown) presses down the disk.
The operation of the disk driver having the rotor balancer of the conventional art constructed as described above will now be explained with reference to FIGS. 2A and 2B.
FIG. 2A is a view showing how the balls are aligned for a disk without a mass eccentricity in an auto balancing unit of a rotor balancer, in accordance with the conventional art. FIG. 2B is a view showing how the balls are aligned to compensate for a mass eccentricity in the auto balancing unit of the rotor balancer, in accordance with the convention art.
That is, as shown in FIG. 2B, for a disk xe2x80x98Dxe2x80x99 having the mass eccentricity, the balls 7 are collected at one side of the space in the ball case 4, correcting the mass eccentricity. FIG. 2A shows a disk xe2x80x98Dxe2x80x99 without mass eccentricity. In this case, the balls 7 are evenly aligned in the space 6 of the ball case 4.
Meanwhile, in case where the disk driver is used vertically, there is following problems due to the gravity force working on the ball 7.
Namely, in case that the disk driver is vertically stood for use, auto balancing, which is however technically difficult, should be favorably made and the balls 7 should be auto-aligned at an early stage.
The auto-alignment refers to a state that the balls 7 are mostly positioned at the outer racing face 8a of the space 6 by virtue of centrifugal force of the spindle motor 3, thereby maintaining balance.
Generally, in order to have a desirable auto balancing, the outer racing face 8a on which the ball 7 travels should have good asperity, concentricity and circularity, by which friction coefficient between the ball 7 and the outer racing face 8a should be minimized.
Meanwhile, in order to stabilize the ball 7 at an early stage, friction coefficient between the ball 7 and the outer racing face 8a should be great so that the disk driver may overcome the gravity force applied to the ball 7 to push up the ball 7 even in its vertically stood-up state.
Therefore, in the conventional art, due to the mutually contradictory characteristics in the auto balancing of the disk driver and the stabilization of the ball, designing was made by sacrificing either one of the two characteristics.
Resultantly, since vibration reduction absolutely affecting the basic capacity of the disk driver takes the priority for designing, the ball balancing is inevitably delayed, so that auto balancing is not made or incompletely made, causing vibration and noise.
Thus, in order to solve the problem, another method is adopted which will now be described with reference to FIGS. 3A and 3B.
FIG. 3A is a partial sectional view showing a construction of an auto balancing unit provided with a protrusion for pushing up a ball in a state that a disk driver is vertically stood up in accordance with a conventional art, and Figure is a plan sectional view showing a construction and an operation of the auto balancing unit of FIG. 3A in accordance with the conventional art.
As shown in the drawings, in a state that the disk driver installed on a substrate 14 is vertically stood up, a protrusion 15 for pushing up the ball 7 is formed on the racing face of the magnet 5, that is, on the inner racing face 8b. 
In other words, there is a gap between the inner racing face 8b and the outer racing face 8a on which the ball 7 travels in a state that the balls 7 are positioned. Referring to FIG. 3B, if a ball 7 is inserted between its front-side ball and its back-side ball and pushed toward the inner racing face 8b, it would contact the protrusion 15 and be bounced up by the protrusion 15, thereby making auto balancing even at a low speed.
In this respect, once the ball 7 is bounced up, it is continuously rotated in a state that it is aligned by the centrifugal force.
However in this method, the most critical problem is a noise generated when the ball 7 is bounced up by the protrusion 15.
That is, though the noise caused due to the unbalance of the ball 7 was solved, but another noise is generated which is irregular and uncomfortable.
Another problem is that as the ball 7 collides with the protrusion 15 repeatedly, the ball 7 is damaged, and as the ball pushed up by the protrusion 15 applies an impact onto the outer racing face 8a, the surface of the ball is damaged so that its balancing performance is degraded.
In addition, in case that the protrusion 15 that pushes up the ball 7 is used for a long time, it is damaged by the impact, failing to exercise its original capacity as originally designed, so that a reliability is degraded.
Moreover, since the mounting unit of the disk in accordance with the conventional art has a structure that the mounting ring 11 is separately installed on the turntable 9 and supported by the spring 12, if its assembly is not accurate or if an impact is applied to the disk driver, the assembling is easily distorted, degrading a reliability of its operation.
Furthermore, in the conventional art, the central portion of the turntable 9 is collapsed for installing the mounting ring 11, which restricts the space for installation of the ball case 4, so that the outer diameter of the ball case 4 is almost the same as that of the turntable 5. In this case, since an optical pick-up unit that moves in the radial direction at the lower surface of the disk is readily collided with the ball case 4, it is very difficult to install the ball case 5.
Therefore, an object of the present invention is to provide a rotor balancer and a disk driver having the rotor that is capable of simplifying a construction of an auto balancing unit for correcting a rotation unbalance when a rotation member is rotated and a mounting unit on which the rotation member is mounted, and of reducing a noise and a vibration.
To achieve these and other advantages and in accordance with the purposed of the present invention, as embodied and broadly described herein, there is provided a rotor balancer including a ball case installed at a rotor for rotating a rotation member and having a circular racing space of which a racing face has different friction coefficients; and a balancing member moved on the facing face of the racing space to automatically correcting unbalance caused when the rotation member is rotated.
In the above rotor balancer of the present invention, as to the racing face of the racing space, the inner racing face near the rotation center of the rotation member has a greater friction coefficient than that of the outer racing face distant from the rotation center.
In the above rotor balancer of the present invention, asperity of the inner racing face is more than 0.7 xcexcm
In the above rotor balancer of the present invention, the balancing member refers to a plurality of metallic ball.
In the above rotor balancer of the present invention, the rotor refers to a turntable on which a disk is mounted in a disk driver for recording/reproducing a signal on and from the disk.
In the above rotor balancer of the present invention, the rotor refers to a motor for providing power for rotating the disk in the disk driver for recording/reproducing a signal on and from the disk.
In the above rotor balancer of the present invention, the rotor refers to a clamper for rotatably fixing the disk when the disk is mounted on the turntable in the disk driver for recording/reproducing a signal on and from the disk.
In the present invention, the disk driver for recording/reproducing a signal on and from the disk has the rotor balancer.
In the present invention, the rotor balancer is provided at the turntable on which the disk is mounted.
In the present invention, on the turntable, there are provided an insert unit into which a central hole of the disk is inserted; and a plurality of mounting spring pieces formed at the insert unit and made of an elastic material as well as having an elastic form so as to elastically support the disk when it is mounted, so that the disk can be mounted accurately and firmly.
In the present invention, the insert unit is integrally formed with the turntable.
In the present invention, the insert unit is separately formed with respect to the turntable.
In the present invention, the mounting spring pieces are formed around the insert unit.
In the present invention, a circle formed by a line formed by a line connecting the outer periphery of the plurality of mounting spring pieces is greater than the diameter of the central hole of the disk to a predetermined degree, so that the disk is inserted into the insert unit by elastically deforming the mounting spring pieces.